FIG. 1 is a functional block diagram showing the structure of prior art short-distance radio communication equipment (referred to as radio communication equipment or a main body of radio communication equipment from here on), which is applied to a vehicle-mounted navigation apparatus, for example. In the figure, reference numeral 101 denotes a display for displaying a map screen generated by a navigation apparatus, a TV picture, or the like thereon, reference numeral 102 denotes an operation button for switching among various functions, reference numeral 103 denotes a panel in which the display 101 and the operation button 102 are accommodated, reference numeral 104 denotes an antenna disposed in the radio communication equipment, for sending and receiving electric waves, reference numeral 105 denotes a sending and receiving circuit for encoding and decoding radio signals to be sent and received by way of the antenna 104, reference numeral 106 denotes a microprocessor (abbreviated as a μcomputer from here on) for controlling the radio communication equipment, reference numeral 107 denotes a sound signal processing circuit for processing a sound signal, reference numeral 108 denotes a TV signal processing circuit for processing a TV signal, reference numeral 109 denotes a navigation signal processing circuit for processing a navigation signal, reference numeral 110 denotes a medium drive mechanism for driving a medium (e.g., a DVD-ROM) in which map data for navigation are stored, reference numeral 111 denotes a video signal processing circuit for processing either a map signal from the navigation signal processing circuit 109 or a TV video signal from the TV signal processing circuit 109 based on a control signal from the μcomputer 106, reference numeral 112 denotes a main body of radio communication equipment including the above-mentioned components from the antenna 104 to the video signal processing circuit 111, reference numeral 113 denotes a microphone for collecting sounds so as to generate a sound signal, reference numeral 114 denotes a speaker for reproducing an audio signal or the sound signal, and reference numeral 115 denotes a TV antenna for receiving TV signal electric waves.
Next, a description will be made as to an operation of the prior art main body of radio communication equipment.
FIG. 2 is a flow chart for explaining the operation of the prior art main body of radio communication equipment. In FIGS. 1 and 2, when a user operates the operation button 102, the radio communication equipment searches for the party at the other end of the radio communication connection (in step ST101), and displays the party with which the radio communication equipment can communicate by radio on the display 101 based on the searching result (in step ST102).
When the user then selects the party with which the radio communication equipment will communicate by radio by operating the operation button 102 (in step ST103), the radio communication equipment starts carrying out radio communications with the selected party (in step ST104). When a sound signal generated by the microphone 113 is to be sent out through radio communications, the sound signal is passed through the sound signal processing circuit 107, the μcomputer 106, the sending and receiving circuit 105, and the antenna 104, and is then transmitted to the party at the other end of the radio communication connection. In contrast, a sound signal from the party at the other end of the radio communication connection flows opposite in direction to the travel of the outgoing sound signal from the radio communication equipment and is input to the sound signal processing circuit 107, and a reproduced sound is then output from the speaker 114.
The μcomputer 106 determines whether the user has performed radio communication end operation by pressing the operation button 102 or the sending and receiving circuit has received a radio communication end signal indicating an instruction of ending the communication operation from the party at the other end of the radio communication connection (in step ST105). If YES, the μcomputer 106 ends the radio communication operation.
The TV signal processing circuit 108 processes a TV signal received by the TV antenna 115, and the video signal processing circuit 111 then generates a video signal, which conforms to the display 101, from the processed TV signal from the TV signal processing circuit 108. When the medium drive mechanism 110 reads map data from a medium (e.g., a DVD-ROM), and generates and delivers a map signal for navigation to the navigation signal processing circuit 109, the navigation signal processing circuit 109 processes the map signal and the video signal processing circuit 111 generates a video signal, which conforms to the display 101, from the processed map signal from the navigation signal processing circuit 109.
As previously mentioned, in the prior art short-distance radio communication equipment, the antenna for radio communication is uniquely placed at a position that seems to be a desired one and that is within or outside the equipment regardless of the performance of the party at the other end of the radio communication connection and radio communication environments. A problem encountered with the prior art short-distance radio communication equipment is therefore that when the performance of the party at the other end of the radio communication connection is bad or the radio communication environment is bad, the radio communication environment remains to be bad fixedly and the radio communication equipment cannot maintain the status of radio communication good.
The present invention is proposed to solve the above-mentioned problem, and it is therefore an object of the present invention to provide short-distance radio communication equipment that can notify that the level of received signals from the party at the other end of the radio communication connection is equal to or less than a predetermined value, automatically change the environment specification of an antenna for radio communication, which is disposed within or outside the radio communication equipment, thereby improving the level of received signals from the party at the other end of the radio communication connection and maintaining the status of radio communication good regardless of the performance of the party at the other end of the radio communication connection and the radio communication environment.